1. Field of the Invention
The present invention generally relates to an image forming device. More specifically, the present invention relates to an image forming device, such as a copying machine, a printer, a facsimile machine, and the like.
2. Background Information
Conventionally, in color image forming devices, the method used in transferring a toner image onto a sheet of paper is by respectively superimposing the black, yellow, magenta, and cyan color toner images onto the transfer belt before combining the toner images thereof onto the sheet of paper.
In this type of image forming device, the toner concentration is adjusted because sometimes due to a degradation of toner or the like, the intended color concentration of an image may not be produced.
A method of adjusting toner concentration is disclosed in Japan Patent Application Publication JP-11-258872, for example. In this method, first, a pattern image is formed using the image forming unit, which is adjusted in order to maintain the intended color concentration. Then, the difference between the color concentration of the pattern image that is actually formed and the intended color concentration is investigated. In the toner concentration information of an image that is formed by the image forming unit, this difference is reflected in order to form images with the intended toner color concentration. The adjustment of the toner concentration of an image to be formed is made by adjusting the bias of the transfer roller, and the like, that is included in the image forming unit.
However, in the conventional method for adjusting the toner concentration, the color concentration on the surface of the transfer belt is not taken into consideration. Therefore, for example, when the color concentration on the surface of the transfer belt changes due to a stain or toner that is attached thereon, proper adjustment of the toner concentration cannot be made.
In view of the above, it will be apparent to those skilled in the art from this disclosure that there exists a need for an improved image forming device. This invention addresses this need in the art as well as other needs, which will become apparent to those skilled in the art from this disclosure.